How much English should you know before you should drive? Inspired by an interaction I had at a toll booth today:

I had missed a merge onto a different highway and had to exit on a small exit that only let you get on and off with coins. I was panicked, as I wasn't sure I had enough coins to do so, but was calmed down by the sign that gave easy directions on how to pay online if you miss the toll and the plaza you can go to for payment. I managed to scrounge together the change and then noticed the man in front of me walking towards my car.

"I don't have enough coins, do you...?" I realized he was asking for change for the toll, which I would have given him if I had extra (it was only $1.10). But I barely managed to get the coins for myself so I explained that I didn't have another dollar in change. He looked as panicked as I had felt, so I pointed out the sign that I saw. He told me that he didn't understand it because he didn't speak enough English (in so many words). I tried to tell him the number of the plaza he should go to to talk to someone, just repeating what the sign said, and he didn't seem to get it. He then drove off without paying; I have no idea if he managed to figure out where he needed to go or if he just gave up.

I understand that this sign isn't a "normal" sign, it isn't stop, do not enter, yield, or any of the ones that I assume come up on any driver's test, but I was a little worried about giving someone a license that couldn't understand English well enough to read some of the signs on the road. On the one hand, my mind automatically revolts at the thought of an English test to drive a car as a way to discriminate against people who don't speak English; on the other hand, I wouldn't want to be on the road with a person that can't read any sign that isn't an "average" sign. I don't know. Thoughts?